1. Field of the Invention
The present invention relates to a power output apparatus. In particular, the present invention relates to a power output apparatus using a double-winding motor, a motor driving method for driving a double-winding motor, and a computer-readable recording medium having a program recorded thereon for allowing a computer to execute motor drive control.
2. Description of the Background Art
A conventional power output apparatus using a double-winding motor is known from Japanese Patent Laying-Open No. 2002-218793. Referring to FIG. 14, this conventional power output apparatus 300 includes a double-winding motor 310, a DC (direct current) power supply 320, inverters 330 and 340 and a capacitor 350.
Double-winding motor 310 includes two three-phase coils 311 and 312. DC power supply 320 is connected between respective neutral points of three-phase coils 311 and 312.
Inverter 330 includes three arms corresponding respectively to the U-phase coil, V-phase coil and W-phase coil of three-phase coil 311 and controls energization of three-phase coil 311. Inverter 340 also includes three arms corresponding respectively to the U-phase coil, V-phase coil and W-phase coil of three-phase coil 312 and controls energization of three-phase coil 312. Capacitor 350 and inverters 330 and 340 are connected in parallel between a positive-pole bus 301 and a negative-pole bus 302.
It is supposed here that a difference in potential between the neutral point of three-phase coil 311 and the neutral point of three-phase coil 312 is represented by V012 and a voltage of DC power supply 320 is represented by Vb. When there is a relation V012<Vb between the potential difference and the power-supply voltage, a DC current flows from DC power supply 320. The DC current flowing from DC power supply 320 is accumulated in one of the U-, V- and W-phase coils of three-phase coil 311 or 312 by switching control of corresponding one of the arms of inverter 330 or 340 so as to finally charge capacitor 350. In other words, one of the U-, V- and W-phase coils of three-phase coils 311 and 312 and corresponding one of the arms of inverters 330 and 340 constitute a voltage step-up converter to increase DC voltage Vb to an arbitrary level and thereby charge capacitor 350.
On the contrary, when there is a relation V012>Vb, a terminal-to-terminal voltage of capacitor 350 is decreased by one of the arms of inverters 330 and 340 and one of the U-, V- and W-phase coils of three-phase coils 311 and 312 that corresponds to the above-mentioned arm so as to charge DC power supply 320.
With the terminal-to-terminal voltage of capacitor 350, inverters 330 and 340 control energization of three-phase coils 311 and 312 to drive double-winding motor 310. Depending on drive conditions of double-winding motor 310, a voltage to be applied to each phase coil of three-phase coils 311 and 312 varies and consequently, potential difference V012 between respective neutral points of three-phase coils 311 and 312 is larger or smaller than DC voltage Vb. Then, there arise the mode of charging capacitor 350 by DC power supply 320 and the mode of charging DC power supply 320 by capacitor 350 as described above.
In power output apparatus 300, DC voltage Vb of DC power supply 320 is increased to an arbitrary level by means of a part of the coils of double-winding motor 310 so as to charge capacitor 350. Then, by the terminal-to-terminal voltage of the charged capacitor 350, double-winding motor 310 is driven. Further, the terminal-to-terminal voltage of capacitor 350 is decreased to charge DC power supply 320.
Japanese Patent Laying-Open No. 2002-218793, however, does not disclose a power output apparatus applied to a hybrid vehicle of mechanical distribution type.